Phosphorus nuclear magnetic resonance (P-31 NMR) is now established as a valuable non-invasive method for investigation of the metabolic state of tissues in vivo.
Nuclear magnetic resonance (NMR) offers the opportunity of selectively examining the nature and function of nucleii of atoms attached to a variety of important biochemicals, of which phosphorus and carbon appear to be currently the most useful and are pivotal in cell metabolism as well. Nuclear mangetic resonance can be most simply described as a pulsed nuclear clock, the rate of which is sensitively dependent upon the chemical environment of the particular nucleus. For example, the atoms of phosphorus, which are attached to a series of key energy-related compounds of the body, give an appropriate signature where the important phosphate compounds in the brain, heart, kidney, liver, and skeletal tissues are the high energy compounds, adenosine triphosphate (ATP), the "energy currency" of the body, and creatine phosphate (PCr), the "short-term energy reserve" of the body, together with low-energy forms of these compounds, adenosine diphosphate (ADP) and inorganic phosphate (P.sub.i). In addition, the sugar phosphate derived from the metabolic pathway activated by glucose metabolism can also be found (F6P, DPG).
In order to realize the full potential of the method, it is important to be able to discriminate between different spatial regions of the tissue under examination. There is a definite need for a more versatile approach than has been available in the past for using NMR imaging techniques to discriminate substantially simultaneously spatially different regions of the tissue under examination, for example, for substantially simultaneously showing the P-31 spectra from different planes through the tissue.